Income Taxes - Provision for income taxes from continuing operations (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Current:
Federal	$ 197	$ 345	$ 401
State	38	36	33
Foreign	14	8	13
Total current	249	389	447
Deferred:
Federal	44	4	(42)
State	(1)	1	(7)
Foreign	0	2	(1)
Total deferred	43	7	(50)
Total provision for income taxes from continuing operations	$ 292	$ 396	$ 397